fix incremental flash, SPIEraseArea isue might erase more then 4k, make min increment 8k
fix incremental flash, SPIEraseArea isue might erase more then 4k, make min increment 8k

devicehive/esp8266-firmware,devicehive/esp8266-firmware,devicehive/esp8266-firmware,devicehive/esp8266-firmware,devicehive/esp8266-firmware